Beta-Hydroxybutyrate dehydrogenase is a phospholipid requiring enzyme which is associated with the mitochondrial inner membrane. The enzyme catalyzes the NAD ion-dependent oxidation of beta-hydroxybutyrate to acetoacetate. BDH is unusual in that unlike other dehydrogenases that have been extensively studied, BDH is a lipid requiring enzyme. The aim of this research program is to prepare BDH in sufficient quantities to carry out a complete documentable amino acid sequence determination of the BDH subunit. The active site peptide of BDH will be investigated using affinity labels and group specific chemical modification reactions. In addition, attempts will be made to identify the lipid binding site of the enzyme using chemical modification techniques and by searches for lipid binding peptides. These studies are essential to the framework for detailed biochemical and biophysical studies of this enzyme.